There are many situations in industry where a flexible sheet material such as paper, cloth, or the like, is passed through different sections of machinery and where the speed at which such material is passed through one of such sections may vary from the speed at which it is passed through another section. It would be highly desirable in such situations to regulate the speed at which the material is passed through the other section to correspond with the speed at which it is passed through the one section so that the material does not either pile up or come into undue tension between sections.
In speaking of "machine," I include the separate mechanisms through which the material is passed continuously, however separated those mechanisms may be.
I am aware of attempts which have been made in the past to solve this problem of variable speed by the provision of devices having levers which contact the loops of material between sections using rheostats to arrange to be operated by the levers thus to cause the speed of the driving motor to be increased so as to take up the additional slack when the speed of the material in a previous section is increased. However, an object to such an arrangement is that the friction involved in operating the rheostat is too great to be operated by anything which is only in lightly touching contact with the moving loop of material between the sections. Another object is that the mechanisms needed for the actuation of such rheostats become mechanically complex and cumbersome, requiring special constructions and the use of nonstandard electrical parts.
It is therefore an object of this invention to provide a device for coordinating the speed of a material through a section of a machine with the speed at which the material is being passed through another section of the machine and to accomplish this smoothly in an effective way without the use of complicated or complex mechanisms. A further object is to provide such a device which will sense the depression of the material between sections with a light touch and which at the same time will positively operate to change the speed of the driving motor for one section so as to coordinate it with the speed of the material being passed through the other section. Still another object is to provide such a device which will accomplish the purpose in a smooth manner and in such a way that only small variations in speed will bring on a necessary adjustment. Other objects and advantages of the invention will be apparent as the specification proceeds.
In my copending application, Ser. No. 455,643 filed Mar. 28, 1974, I describe a device of the character above referred to which includes an annular coil of wire having electrical impedance and mounted on a tiltable structure, and an annular raceway beside the coil with a ball which stays at the lowest point in the raceway and so produces variation in the impedance of the coil between the ball and an end of the coil as the structure is tilted.